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Transcranial direct current stimulation

3.
OUTLINE
What CL Psychiatrists Need to Know
Complications of tDCS
Efficacy of tDCS
Indications/Contraindications for tDCS
Mechanism of Action of tDCS
What is tDCS?
Brief History of Electrical Stimulation

5.
EARLY BRAIN STIMULATION
Ancient civilizations applied the
electric torpedo fish to the head
to treat illness (Kellaway 1946)
Kellaway P. The part played by electric fish in the early history of
bioelectricity and electrotherapy. Bull Hist Med 1946; 20(2): 112-137.

12.
CONSTANT CURRENT
tDCS is not pulsatile, so there
is no pulsewidth variable.
Voltage varies to maintain
current constant (V = IR)
Current strength is varied
depending on desired intensity
of stimulation.
Current duration is varied
depending on desired total
charge.
Nitsche MA et al. TDCS: state of the art 2008. Brain Stimulation 2008;
1: 206-223.

41.
 VNS was approved for pharmaco-resistant epilepsy in
Europe in 1994 and in the US in 1997.
 Anecdotal clinical observations of mood improvement
in epilepsy patients after VNS implantation.
 Role for VNS therapy in depression??
July 2005:
FDA approval as an adjunctive treatment of severe,
recurrent unipolar and bipolar depression.

46.
2 years
Results remained similar:
- response rate of 42% and
a - remission rate of 22%
- Overall response
rate : 40-45% long
term
- 81% of patients
who elect to keep
their device active
at 2-years.
Additional 25% of patients
(separate from the 42%),
improvement in symptoms of
25 -49%, which is short of
responder status
meaningful in the context of
severe, unremitting MDD?

49.
 The FDA approved the VNS implant for patients with
chronic or recurrent depression, (uni/bipolar) with a
history of failure of their depression to respond to at
least 4 antidepressant interventions.
 ECT failure is not a requirement to be eligible for VNS

50.
 Indication
 TRD patients with bipolar and unipolar depressive
episodes as a long term adjunctive treatment option
 Failure to respond to ECT is not a prerequisite for VNS
eligibility,
 It may be appropriate to use ECT as an acute treatment
for severe depression to be followed by VNS as a long
term maintenance intervention.

51.
Relative
Contraindications
 Not approved for psychotic
MDD or the depressed
phase of SAD.
 Paranoid ideation
 Unstable axis II disorders
 Borderline personality
disorder or other
disorders,
 Not studied in pregnancy-
 non-systemic treatment
 potential effects on fetus should
be limited
 Limitations in post-surgery MRI
 MRIs spine/joints prohibited.
 MRI brain possible w/ special
send-receive coils. (otherwise a CT scan
would need to substitute for an MRI)
 Dissatisfied?
 Could be switched off (the implant left
in place)
 Pulse generator could be
explanted.
 The electrode is left in situ--
adhesions around the vagus nerve
itself might increase risk of injury
during removal .
 Precautions with MRI remain in
place indefinitely
Special Precautions

53.
Surgery
post 2 wks
•0.25 mA titrations in
current so that a
target dose of 1.0 mA
might be achieved at
the end of the first
month.
Weekly for
1 month
Q 2weeks for
1 month
Month 3
•Monthly visits if effective
•amplitude 1.0-1.5 mA range
and no improvement 
increase the duty cycle at
the juncture by adjusting
the on-off schedule.
Significant proportion of
responders to VNS only
emerge in the second 6
months of stimulation and
a full VNS trial may require
at least 12 months

56.
 VNS device can remain functioning for up to 8 years.
 Patients are unable to adjust the treatment settings
independently.
 In the one year pivotal study (Rush et al. 2005)
 Continuation rate at 1 year was 90%.
 3% discontinued secondary to adverse events
 implant related infection,
 hoarseness,
 lightheadedness,
 postoperative pain
 chest and arm pain.
 7% -- lack of efficacy or other reasons.
 At 2 years (Nahas et al 2005)
 >80% of patients had device in place and functioning
 Most subjects electing to discontinue VNS because of lack of efficacy
rather than side effects.

57.
 Safe and effective treatment in TRD
 FDA approved.
 Better results when used long term (12
weeks-1 year)
 Better results when combined with
meds. (can be combined with any meds
including MAOIs).
 Safe with ECT but it needs to be turned
off.
 No cognitive side effects.
 Can be used both for unipolar and
bipolar depression
 Dosing can be done in an outpatient
setting.
 Cautions
 Surgical risks
 Current and future MRI safety
 Side effects
http://www.utsouthwestern.edu/newsroom/news-releases/year-2005/vns-therapy-
for-treatment-resistant-depression-proves-effective-for-some-patients.html
Vagal Nerve Stimulation for Seizures. Textbook of Stereotactic and Functional
Neurosurgery. pp 2801-2822

58.
 Safe and efficient neuromodulation modality in TRD.
 Over the longer term at one and at two years the
results observed with VNS appear reasonable in terms
of realistic expectations for this population.
 A controlled post marketing study as suggested by the
FDA is being conducted by the device manufacturer.
 Significant promise to treat TRD as a long term
treatment.